The invention relates to an illuminating device for a photographic enlarging or copying apparatus.
Such illuminating devices are designed for the largest nominal format to be illuminated of an original copy to be copied. However, all smaller formats must also be copied. For this purpose the corresponding copy holders inserted into the illuminating apparatus are equipped with masks, adapted to the individual formats to be copied, which hold back the light of the non-utilized, illuminated format surface or reflect it into the illuminating device. Since the light yield in copying smaller formats than the nominal format is small, illuminating equipment has been developed with interchangeable lighting compartments adapted to the individual formats in cross section, making possible an optimum light yield for original copies of various formats. In the known illuminating devices, the interchange of these lighting compartments is connected with a certain expenditure, since their location in the respective illuminating devices is obtainable with difficulty and apparatus parts must therefore be removed or lifted up, the lighting compartment must be removed and the lighting compartment adapted to the copy format inserted in place of the removed compartment. In addition, there exists the danger that the lighting compartments not directly inserted into the illuminating device may become dirty or damaged by careless storage. The switching of the lighting compartments can be advantageous with respect to cutout enlargements but are hardly ever utilized in the known devices because of the complications in such an exchange.
Illuminating devices have indeed become known wherein a quick alteration of the cross section of a lighting compartment is possible without the necessity of removing apparatus parts, so that the given drawbacks no longer pertain. Thus, DT-OS 2,326,900 = U.S. Pat. No. 3,831,021, discloses an illuminating device for an enlarging apparatus wherein the cross section of a lighting compartment is continuously variable. The subject matter of DT-OS 2,238,944 is a lamp housing for enlarging apparatus, wherein the shape of a lighting compartment for the purpose of a format adaptation is transformable from a truncated pyramidal shape into another truncated pyramidal shape.
However, both of the aforementioned illuminating devices have the drawback that they may be utilized for only a certain shape of a lighting compartment. This shape, in the case of DT-OS 2,326,900, can only be that of a parallelepiped, in the case of DT-OS 2,238,944, that of a truncated pyramid, and in an in between case, that of a parallelepiped. But in the event that a lighting compartment has a form different therefrom, e.g. a mixes parallelepiped and truncated pyramidal shape, both suggestions for a solution are inapplicable.
A further drawback of such illuminating devices consists in that the light mixing or the light distribution can be ideal only for a single original copy format. In illuminating devices for enlarging and copying appratus, it is known to provide at the light admitting and/or emerging surface of the lighting compartment, diffusing lenses, which have various densities and various cross-sectional shapes, depending on the mixing and distributing conditions of the light upon admission to the particular lighting compartment. The density and/or the cross-sectional shape of the diffusing lenses vary particularly in one and the same apparatus with each lighting compartment adapted to a particular original copy format.
The object of the invention is to provide an illuminating device of the previously stated type, wherein lighting compartments of various cross-sections and/or various shape are provided, in a manner convenient for an operating technician, for the individual original copy formats to be illuminated, the light mixing and/or distribution being maximizable for each format